The assignee of the present invention has for some time sold multiple pocket, microprocessor controlled, chargers for relatively rapid (less than one hour) charging of battery packs for battery powered surgical tools. Examples are the present assignee's System II charger Models 298101 through 298106 available from Stryker Corporation of Kalamazoo, Mich. Such chargers are variously provided with two or four battery receiving pockets. These chargers incorporate microprocessor controlled charging circuitry which, in addition to charging such battery packs, is capable of testing and displaying various conditions of each battery pack inserted therein, namely that the battery pack is faulty and requires replacement, the battery pack is in the process of being charged or the battery pack has been charged and is ready for removal from the charger and use in the corresponding surgical tool. The displays are, for each pocket, energizable lights labelled "REPLACE", "CHARGE", and "READY".
A battery pack of the kind included in this prior system is insertable into each of a family of surgical power tools, for example wire drivers, drills, reamers, and various saws, to power same for use in a variety of surgical procedures.
In general, the aforementioned surgical tool battery and battery charger system has performed satisfactorily. However, in a continuing effort to improve, the present invention has been developed.
As one aspect of the present invention, the present inventors have noted the following. Different types of battery operated surgical tools have sharply differing energy requirements. On the other hand, it is desirable to have each battery plug into the handle of all of the surgical power tools in the family. For example, tools such as a wire driver or a sternum saw are typically only used for a very short time in a given surgical procedure (typically a minute or so for a wire driver and 10 to 20 seconds for a sternum saw). It is desirable for such small energy requiring surgical tools to be able to use a battery pack which has a lesser charge storage capacity, namely one with fewer battery cells and a physically smaller size. Some other battery operated surgical tools are used for a considerably longer time in a given surgical procedure and may in some instances be required to use energy faster in carrying out their part of the surgical procedure. In those surgical tools, greater energy storage capacity is required, thereby requiring the battery pack to contain more battery cells and hence to be physically larger, having a larger rear portion.
Moreover, the present inventors have found that surgeons wish to be able to recharge a battery for any surgical power tool in the family in no more than an hour, regardless of the level of energy demand for the particular tool which they plan to use. However, it is possible to damage a battery pack, particularly of nickel cadmium (NiCad) type, if a battery pack of low energy storage capacity is charged at an amperage which would be optimal for charging a NiCad battery pack of larger energy storage capability. On the other hand, it would unduly delay charging of a NiCad battery pack of larger energy storage capacity, to charge same at an optimum rate for a NiCad battery pack of substantially lower energy storage capacity. This problem is true when, for example, battery packs normally rated at 500 and 1,000 milliampere hour storage capacity are to be used with different members of the same surgical power tool family (e.g. wire drivers, saws, drills and reamers for example). Moreover, surgeons and their support staffs are of course expected to direct their primary attention at the surgical problems involved in a particular surgical procedure, rather than being expected to be expert in the art of battery charging or to pay attention to charging requirements of different capacity battery packs.
It is an object of the present invention to overcome this set of conflicting problems. Purposes of various aspects of the present invention are to provide battery packs of widely differing energy storage capability all shaped for reception in the common handle-configuration found in a family of different, battery powered, surgical tools and all alternatively receivable in a single battery charger, which charger is capable of differentiating between relatively high and relatively low energy storage battery packs and automatically, without need for instruction from the surgeon or his staff, recharging differing battery packs each at its own optimum charge rate, so as to permit charging of all of the differing battery packs in a short required time (such as an hour) without damaging the smaller energy storage capacity battery packs.
Other objects and purposes of the invention will be apparent to persons acquainted with apparatus of this general type upon reading the following specification and inspecting the accompanying drawings.
According to one embodiment of the present invention, there is provided a battery charger for alternately receiving batteries having substantially different charging rate requirements in which the charger has contacts engaged by a battery pack to be recharged, for the purpose of carrying out such recharging. However, there is a difference in at least one of the contacts as between the high and low charge rate battery packs such that the battery charger automatically applies charging current at different levels to differing battery packs, so as to automatically charge the high and low energy storage capacity battery packs at corresponding high and low charge rates.